Another advantage of using these classes is that it can make your code easier to adapt to other data sources. For example, if you use QSqlTableModel and later decide to use XML files to store data instead of a database, it is essentially just a matter of replacing one data model with another.

If you modify a primary key, the record might slip through your fingers while you are trying to populate it.

The SQL Relational Table Model

QSqlRelationalTableModel extends QSqlTableModel to provide support for foreign keys. A foreign key is a 1-to-1 mapping between a field in one table and the primary key field of another table. For example, if a book table has a field called authorid that refers to the author table's id field, we say that authorid is a foreign key.

The screenshot on the left shows a plain QSqlTableModel in a QTableView. Foreign keys (city and country) aren't resolved to human-readable values. The screenshot on the right shows a QSqlRelationalTableModel, with foreign keys resolved into human-readable text strings.